Activated Charcoal-Mediated Hydroxylation Under Very Mild Conditions: Conversion of Physalin B into 25-Hydroxyphysalin B.

Activated charcoal treatment of physalin B, a 13, 14-seco-16,24-cyclosteroidal constituent of Physalis alkekengi, in MeOH at room temperature yields a product possessing a hydroxy group at the α-position of the δ-lactone carbonyl function, namely 25-hydroxyphysalin B, in high yield.